Ann. Limnol. - Int. J. Lim. 39 (3), 273-280

Pourriotia carcharodonta, a new genus and species of monogonont from subantarctic Îles Kerguelen (Terres Australes et Antarctiques Françaises)

W.H. De Smet

University of Antwerp, R.U.C.A.-campus, Department of Biology, Section Polar Ecology, Limnology and Palaeobiology. Groenenborgerlaan 171, B-2020 Antwerpen, Belgium. E-mail : [email protected]

Pourriotia carcharodonta gen. et sp. nov. is described from freshwater plankton collected at the subantarctic Kerguelen islands. The new taxon is provisionally placed in the Notommatidae. Main diagnostic characters separating the new taxon and the other genera of the family are provided by the morphology of the trophi. Apical rami chambers with toothed inner margin and blunt projection on outer margin. Apical rami teeth and subuncinal teeth with accessory spines. Proximal margin of major uncinal teeth firmly connected to distal margin of apical chambers, forming grasping unit. Fulcrum dumb-bell-shaped. Information is presented on the trophi structure of the genus Pleurata (Notommatidae).

Keywords : Rotifera, Notommatidae, Pourriotia carcharodonta, new genus, new species, Kerguelen Islands, subantarctica, fre- shwater, Pleurata.

Introduction WNW from the base Port-aux-Français, at an altitude of 70-80 m a.s.l. and a distance of 7.4 km from the sea. The subantarctic Kerguelen archipelago (48°58’- It is a fairly large lake with a surface area of 84.6 49°73’ S, 68°72’- 70°58’E) is part of the Terres Aus- 104 m2, and an average depth of 23 m. According to trales et Antarctiques Françaises (T.A.A.F.). It is situa- Maire (1985) it is oligotrophic, neutral to weakly alka- ted in the Southern Indian Ocean (Fig. 1), c. 5000 km line with buffering capacity almost zero. It is tho- from South Africa and Australia, and c. 2000 km from roughly mixed up to its maximum depth of 43 m, and the Antarctic Continent. The area is characterized by a never stratified due to the continuing strong winds and cold temperate climate with a strong maritime influen- the small amplitude of the watertemperature. Littoral ce (Stonehouse 1982). A recent study on the plankton samples (plankton, submerged mosses, hygropsam- from some freshwater habitats at the main is- mon, Aufwuchs) were sampled in February 1998 and land Grande Terre (De Smet 2001), revealed 38 mono- January 2002, in the southern corner of the lake, off the gonont taxa, of which 33 were new records for Îles cabins. Plankton was collected by a horizontal haul, Kerguelen. Among these taxa were two species listed using a 40 µm mesh plankton net. All samples were as «Incertae sedis». One of them was represented by a fixed on the spot with formalin up to a concentration of sufficient number of specimens to be described in de- 3 %. were examined and drawn with a Leitz tail herein. Orthoplan microscope equipped with camera lucida. Preparation of trophi for light and scanning electron Material and methods microscopy (SEM) was done following De Smet (1998), using dilute NaOCl solution. SEM was perfor- Lac Supérieur (formerly called Lac Studer 1) is lo- med with a Philips SEM 515 microscope operated at cated (Fig. 1) in the valley Val Studer, some 15 km 20 kV.

Article available at http://www.limnology-journal.org or http://dx.doi.org/10.1051/limn/2003022 274 W.H. DE SMET (2)

Diagnosis Body elongated, illoricate. Corona strongly oblique. Head with pseudorostrum. Foot terminal, with short toes. Subcerebral glands present. Three salivary glands : one contained in mastax distally, two large pyriform and stalked laterally. Trophi modified virga- te. Rami with elongate basal and subbasal chambers, and apical chambers with toothed inner margin and blunt projection on outer margin. Apical rami teeth with accessory spines. Fulcrum dumb-bell like in dor- sal/ventral view. Unci firmly connected to apical chambers, forming grasping unit. Subunci present, teeth with accessory spines. Head of manubria com- posed of three chambers. Epipharynx two large boot- shaped plates. The new taxon can not be confused with any other genus. Pourriotia carcharodonta gen. et sp. nov. (Figs. 2- 17) Material examined Holotype : a parthenogenetic female in a perma- nent, glycerin glass slide mount deposited in the Ko- ninklijk Belgisch Instituut voor Natuurwetenschap- pen (K.B.I.N.), Brussels, reg. nr. I.G. 29.824, RIR145. Paratypes : one slide with one paratype in K.B.I.N., reg. nr. I.G. 29.824, RIR146 ; 6 slides with one parthe- nogenetic female, and 2 stubs each with one trophi pre- paration for SEM in the Department of Biology, Uni- versity of Antwerpen. Type locality Lac Supérieur (formerly called Lac Studer 1) in val- ley Val Studer, Courbet peninsula, Grande Terre, Îles Kerguelen, Southern Indian Ocean (T.A.A.F.). Obtai- ned from littoral plankton taken near cabins on 4 Fe- Fig. 1. Upper : map showing Îles Kerguelen in relation to the conti- bruary 1998. nents and some other subantarctic islands. Lower : map of Îles Kerguelen with sampling area of the Val Studer indicated.

Description of new genus and species Pourriotia gen. nov. Type species Pourriotia carcharodonta sp. nov., by monotypy. Etymology The genus is dedicated to Prof. Dr. Roger Pourriot, in recognition of his important contributions to the stu- Fig. 2. Pourriotia carcharodonta gen. et sp. nov., holotype lateral dy of Rotifera. view. (3) POURRIOTIA CARCHARODONTA GEN. & SP. NOV. (ROTIFERA) FROM KERGUELEN 275

Figs. 3-8. Pourriotia carcharodonta gen. et sp. nov., female. 3. dorsal view, 4. lateral view, 5. trophi, ventral view, 6. trophi, dorsal view, 7. subunci, 8. apical rami chambers. Scale bar : 3, 4 : 50 µm, 5, 6 : 10 µm, 7, 8 : 1 µm.

Etymology or less gradually narrowing to foot ; tail indistinct. La- The specific name carcharodonta is derived from teral antennae not seen. Foot medium long, c. 1/5 of to- the Greek «karcharodous», meaning with sharp teeth, tal length, with two cylindrical pseudosegments of and refers to the shape of the unci, subunci and apical equal length. Toes equal, c. 1/12-1/15 total length, al- rami teeth. most conical, inner and ventral margins slightly undu- late in dorsal and lateral view respectively ; tips of toes Description tubular. Two large colourless frontal eyespots. Brain Female (Figs 2-4). Cuticle soft. Body fusiform in large, saccate. Retrocerebral sac very large, at poste- dorsal view, broadest near mid length ; in lateral view rior of brain. Subcerebral glands large. The outlets of more or less conical. Head continuous with trunk, lar- the ducts of the retrocerebral sac and/or subcerebral ge, about 1/3 of total length, with vesicle-shaped pseu- glands probably opening through the antero-median dorostrum. Corona strongly oblique, with ventral in- papillae. Mastax with three salivary glands : a single dentation near middle, mouth opening at posterior mar- one contained in the mastax wall and bulging poste- gin ; auricles absent. A short papilla with long cilia la- riorly, and two large stalked pyriform glands laterally terally on both sides of pseudorostrum. Some speci- from mastax, almost extending to middle of body. Sto- mens with two close-set small papillae antero-medially. mach and intestine not separated by constriction. Gas- Dorsal antenna in depression near posterior of brain. tric glands roundish to rounded triangular, short-stal- Trunk without distinct folds, broadest anteriorly, more ked. A well-differentiated bladder is apparently absent. 276 W.H. DE SMET (4)

Figs. 9-17. Pourriotia carcharodonta gen. et sp. nov., trophi, SEM photographs. 9. complete set of trophi, ventral view, 10. ibidem, dorsal view, 11. ibidem, dorso-lateral view, 12. ibidem, ventro-lateral view, 13. complete set of trophi, dorso-apical view, 14. detail, ventral view, 15. detail, dorsal view, 16. apical rami chambers, dorsal view, 17. subunci, ventral view. b : basal ramus chamber, s : subbasal ramus chamber, dc : dorsal manubrial chamber, mc : medial manubrial chamber, vc : ventral manubrial chamber. Scale bars : 9-15 : 10 µm, 16, 17 : 1 µm. (5) POURRIOTIA CARCHARODONTA GEN. & SP. NOV. (ROTIFERA) FROM KERGUELEN 277

Pedal glands club-shaped, foot length. Vitellarium mus chamber 3.8-3.9 x 1.6-1.7 µm, fulcrum 6.2-6.9 with 8 nuclei. µm, uncus 6.5-7 µm, manubrium 10-11 µm, apical Trophi (Figs. 5-17) modified virgate, small, almost chamber 3.8-3.9 x 1.6-1.7 µm, subuncus 4.4-4.7 µm, symmetrical. Rami and fulcrum lying in the same pla- epipharynx plate 3.7-4 µm. ne ; the mallei form a fairly small angle with the incus. Comments Rami outline lyrate. Rami more or less flat, not recur- The new taxon shows a combination of peculiar cha- ved dorsally, with conspicuous apical, basal, and sub- racters which make its affiliation problematical. The basal chambers ; small alulae. Basal and subbasal well developed retrocerebral apparatus is of the No- chambers elongate (b, s ; Figs. 14, 15). Opening of tommata-type, and the corona likewise reminds of the subbasal chambers rounded, opening of basal cham- Notommatidae (de Beauchamp 1907, 1965). The tro- bers elongate-triangular (Fig. 15). Inner margins of ba- phi apparently possess elements of both the virgate ty- sal and subbasal chambers without teeth ; a distinct pe, as found in Notommatidae, and the forcipate type, longitudinal crest extending over the whole length of characteristic of the Dicranophoridae. A fairly long the rami dorsally. Apical chambers (Figs. 8, 16) with fulcrum, distally enlarged for the attachment of the hy- superimposed teeth on inner margin, and blunt projec- popharyngeal muscle, is a feature common to many tion on outer margin. Teeth composed of 3 (left) or Notommatidae. However, the dumb-bell shape as 2 (right) curved sharp teeth, each with small accessory found in the new species is unique ; a similarly enlar- toothlet at their base ; ventral teeth smallest. Distal ged spoon-shaped distal end of the fulcrum is found margin of lateral projections firmly connected to only in Rousseletia corniculata Harring, 1914. The en- proximal margin of head of major uncinal teeth by li- larged proximal part of the dumb-bell-shaped fulcrum gaments ; lateral projections apparently with small in Pourriotia suggests the presence also of well deve- opening laterally. The basal part of the apical chambers loped abductor muscles, connected to the posterior shows a small indentation near the juncture with the edges of the rami and the alulae, as found in Dicrano- basal chamber. Fulcrum pointing towards posterior, ra- phoridae. Up till now, large epipharyngeal plates in the mus length, outline dumb-bell-shaped in dorsal view. ventro-lateral walls of the mastax were reported in the The broadened distal end is terminally rounded, recur- notommatid genus Pleurata only. Unci displaying two ved dorsally and spoon-shaped ; its ventral surface is or more teeth, likewise are common to many notom- smoothly rounded. The broadened proximal end is mo- matids, although SEM has shown (De Smet 1997, and re or less triangular, slightly hollow ventrally and kee- unpubl.) that a tooth formula of 2-3/3-3 is not rare in led dorsally ; its composing sclerite bodies are coarse Dicranophorus too, where it is a plesiomorphic trait. and distinct. Unci long, c. 2/3 manubrium length, pla- Tapering uncinal teeth without offset head are found in te-shaped, composed of almost completely fused teeth both families. Rami lying in the same plane as the ful- with free head, and subuncus. Two (right) to three crum, is one of the main characters of the forcipate tro- (left) sharp and incurved teeth of unequal length : ven- phi of Dicranophoridae, although it is to be found in tral teeth smallest ; teeth tapering, without offset head. some notommatids too. Dorso-ventrally flattened and Inner side of unci with prominent rib. Dorso-basal part elongate basal and subbasal chambers, a common fea- of unci broadening towards manubria. Subunci (Figs. ture in dicranophorids, are shared with some notom- 7, 17) composed of two slightly curved teeth of une- matids (e.g. Pleurata Figs. 18, 19). Similarly to dicra- qual length connected basally ; each tooth bears a nophorids (e.g. Dicranophoroides trophi in De Smet weakly developed accessory spine. Manubria approxi- 1997 : Plate 1), the rami are terminated by an apical mately incus length, rod-shaped with short triangular chamber bearing teeth at their inner margin. The ac- head composed of ventral, medial and dorsal chambers cessory spines, shown by the teeth of the apical cham- (vc, mc, dc ; Figs. 14), and ventrally decurved cauda ; bers and subunci, have not been demonstrated in any ventral chamber smallest ; opening of ventral and me- other rotifer taxon. The unci are firmly connected to dial chambers ventrally at inner side of manubria, ope- the distal margins of the apical chambers, and form a ning of dorsal chamber at outer side (Figs. 14, 15). The grasping unit. The lateral projections of the apical epipharynx consists of two large boot-shaped plates chambers are interpreted as a specialisation, allowing ventrally from rami (Fig. 14) ; plates connected to un- for a broader attachment to the unci. This situation ci by ligaments. whereby the unci are fused to the apical chambers or Measurements rami tips is absent in Notommatidae (with the excep- (N=10) Total length 123-164 µm, toe 10-11 µm ; tion of Tylotrocha monopus (Jennings, 1894) ?), where (N = 2) trophi 12-13 µm, ramus 6.5-6.8 µm, apical ra- unci are hinged ventrally to the rami(tips). In Tylotro- 278 W.H. DE SMET (6) cha the mallei and rami are fused to a dome-shaped sent in the new taxon. Another important difference structure, with mallei no longer divisible in unci and between both taxa is in the morphology of the manu- manubria (Harring & Myers 1924). However, SEM in- bria. Those of Pourriotia have an almost straight, rod- vestigations are required as unci may also be absent shaped shaft with incurved caudum, and short head (see e.g. Dorystoma, Rousseletia). A fusion between composed of three chambers each with opening. The unci and rami is seldomly encountered in Dicranopho- manubria in Pleurata s. str. are more or less curved ridae (Parencentrum, ? Myersinella), which usually with flattened head composed of elongated medial and show unci pivoting on the rami tips or bases of the ra- dorsal chambers (mc, dc ; Figs. 21), and a distinctive mus lock. lamellar ventral chamber (vc ; Figs. 18-20), located The characteristics of Pourriotia are largely inter- medially or more distally according as the species. The mediate between those of Notommatidae and Dicrano- opening of the medial chamber is situated on a level phoridae. However, the forcipate trophi of the latter with or distally to (om ; Fig. 20) the ventral chamber, lost their pumping action and became adapted for pre- depending on the species. Both Pleurata s. str. and hension only. The new taxon possesses trophi with Pourriotia show very large epipharyngeal plates, a both virgate fulcrum and rami forming pincers in their feature not found in other rotifer species. Some rele- anterior part, as found in many genera within Notom- vant taxonomic differences at the generic level concer- matidae, and hence it is placed in this family. However, ning the soft body parts are obvious also. Pourriotia seeing that the Notommatidae is an unsatisfactory as- has two frontal eyespots, and Pleurata s. str. is provi- semblage of diverse taxa (Nogrady et al. 1995) and al- ded with a cerebral eye (reported absent in P. tyleri by most surely polyphyletic, the allocation of Pourriotia Nogrady et al. (1995), but apparently shown in should be considered provisional, and reevaluated Fig. 15b in Koste et al. (1988)). Subcerebral glands when new information, in particular sequencing analy- and a pseudorostrum are present in Pourriotia only. sis, becomes available. Other features distinguishing the two genera are the slender and less sclerified trophi (Figs. 18-22) and dis- The vesicle-shaped pseudorostrum of unknown tinct alulae in Pleurata s. str., and the large and stalked function is very rare in Rotifera, and has only been ob- lateral salivary glands present in the new taxon but ab- served in Wulfertia kindensis (Proalidae) described sent in Pleurata s. str. from Birma by Koste & Tobias (1990). Distribution and ecology The trophi of Pourriotia show a superficial resem- blance with those of some members of the genus Pleu- Specimens of Pourriotia carcharodonta were obtai- rata (Notommatidae). The latter genus was established ned in low numbers from littoral plankton of lake Su- by Nogrady & Pourriot (Nogrady et al. 1995) to ac- périeur. It could not be found in other samples inclu- commodate tithasa Harring & Myers, ding submerged mosses, Aufwuchs consisting of fila- 1922, N. trypeta Harring & Myers, 1922, N. tyleri Kos- mentous algae, and hygropsammon taken at the sam- te, Shiel & Tan, 1988, chalicodis Myers, pling site. The species was found during the sampling 1933, P. thura Myers, 1933 and P. vernalis Wulfert, campaign of February 1998 only. An intensive sam- 1935, and should include Proales uroglenae de Beau- pling effort of different habitats at the type locality in champ, 1948 also (De Smet 1996). However, the tro- 2002 did not yield a single specimen. The bottom at phi of P. tithasa and P. thura are very different, which the sampling site was stony with gravel and some sub- suggests that both species should not be retained in merged mosses. Watertemperature 11°C, pH 7.5, Pleurata ; the other members of the genus are referred conductivity 60 µS cm-1, total alkalinity titer as Pleurata s. str. hereafter. Close analysis reveals im- 0.24 mmol l-1. No food items were observed in the sto- portant differences between Pleurata s. str. and Pour- mach or intestine. The species was accompanied by a riotia. Pleurata s. str. lacks the characteristic toothed fairly rich rotifer fauna dominated by Keratella sancta apical chambers of Pourriotia. The unci are small and Russell, and crustaceans with the copepod Pseudo- weakly developed in Pleurata s. str. (the uncinal appa- boeckella volucris Kiefer as dominant (De Smet, ratus of the species shown in Figs. 21-22 with 5-6 short 2001). The phytoplankton was characterized by Bo- and loosely bound teeth and 1-2 long, rod-shaped ele- tryococcus braunii Kützing and Mougeotia sp. ments). The fulcrum in Pleurata s. str. is almost rod- The shape of the trophi suggest that the new taxon shaped and slightly expanding distally in dorsal view, might be a predator or ectoparasite. The peculiar apical instead of dumb-bell-like with spoon-shaped end dis- rami chambers with their sharp curved teeth, may tally. Moreover the fulcrum of the species shown in function in the attachment to or holding of some orga- Fig. 18-22 displays an opening distally, which is ab- nism. The long and distally spoon-like enlarged ful- (7) POURRIOTIA CARCHARODONTA GEN. & SP. NOV. (ROTIFERA) FROM KERGUELEN 279

Figs. 18-22. Pleurata (s.str.) sp., trophi, SEM photographs. 18. complete set of trophi, ventral view, 19. ibidem, dorsal view, 20. ibidem, ventro-caudal view, 21. detail, dorso-apical region, 22. detail, ventro-apical region. dc : dorsal ma- nubrial chamber, mc : medial manubrial chamber, vc : ventral manubrial chamber, om : opening of medial chamber, u : uncinal apparatus. Scale bars : 10 µm.

crum, and the large epipharyngeal plates supporting Rotifères, Gastrotriches, Kinorhynques. T. IV(3). Masson et Cie., the ventro-lateral walls of the mastax are evidence of a Paris : 1225-1379. De Smet W.H. 1996. — Rotifera 4 : The Proalidae (). strong pumping action to suck out the contents of some In H.J. Dumont & T. Nogrady (eds.) : Guides to the Identification prey or host. of the Microinvertebrates of the Continental Waters of the World 12. SPB Academic Publishing, The Hague, The Netherlands : Acknowledgements 102 p. De Smet W.H. 1998. — Preparation of rotifer trophi for light and I gratefully acknowledge the «Institut Polaire Français» for the scanning electron microscopy. Hydrobiologia, 387/388 (Deve- logistic and financial support, and the Science Foundation Flanders lopm. Hydrobiol., 134) : 117-121. (F.W.O.) for additional funding. The present study is part of the De Smet W.H. 2001. — Freshwater Rotifera from plankton of the Terrestrial Ecology Program Biosol n° 136 (Dr. Y. Frenot, Station Kerguelen Islands (Subantarctica). Hydrobiologia, 446/447 (De- Biologique Paimpont). The Laboratory of Cell Biology and velopm. Hydrobiol., 153) : 261-272. Histology provided the necessary SEM facilities. De Smet W.H. 1997. — Dicranophoridae. In De Smet, W.H. and R. Pourriot, Rotifera 5 : The Dicranophoridae (Monogononta) and References the Ituridae (Monogononta). Guides to the Identification of the Microinvertebrates of the Continental Waters of the World 12, de Beauchamp P. 1907. — Morphologie et variations de l’appareil H.J. Dumont & T. Nogrady (eds.) : SPB Academic Publishing, rotateur dans la série des Rotifères. Arch. Zool. expér., 6 : 1-29. The Hague, The Netherlands : 344 p. de Beauchamp P. 1965. — Classe des Rotifères. In P-P. Grassé : Harring H.K. & Myers F.J. 1924. — The rotifer fauna of Wisconsin. Traité de Zoologie. Némathelminthes (Nématodes, Gordiacés), II. A revision of the notommatid rotifers, exclusive of the Dicra- 280 W.H. DE SMET (8)

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